Near-field enhancement of the mid-infrared field and its control by using metal nano-structures

中红外光为探测微观分子结构和高选择性地激发分子振动提供了强有力的工具。因此，中红外范围内的场增强可能有助于开发分析大分子构象和控制分子运动/反应的方案。在本项目中，我们研究了金属纳米结构对中红外电磁波的共振增强，通过透射谱和电磁场分析，阐明了增强近场的光谱/时间响应。利用工作在中红外范围内的扫描式近场光学显微镜测量了增强近场的空间分布。我们还通过数值模拟研究了自由度对增强近场时间波形整形的影响。

Mid-infrared light provides powerful tools in probing microscopic molecular structures and in exciting molecular vibrations with high selectivity. Field enhancement in mid-infrared range, therefore, may help developing schemes of analyzing conformations of macromolecules and controlling molecular motions/reactions. In this project, we investigate metal nano-structures which bring about resonant enhancement of the mid-infrared electromagnetic waves.By transmission spectroscopy and the electromagnetic field analyses, the spectral/temporal responses of the enhanced near-fields are clarified. The spatial distribution of the enhanced near-field is measured by using the scanning-type near-field optical microscopy working in the mid-infrared range. We also investigate by numerical simulations the degree of freedom in shaping the temporal waveform of the enhanced near-field.